The Education Bureau set off a storm by warning a week ago that teachers risked disqualification if they encouraged students to engage in pro-independence talk. Education minister Eddie Ng Hak-kim later said students could only hold such discussions under the supervision of teachers and within the limits of the Basic Law.

Ng has ruled out setting guidelines for schools, leaving it to the “professionalism” of teachers and principals. But critics are calling for more clarity on the restrictions, with a Basic Law expert asking the government to specify whether promoting independence is indeed unlawful.

The Post found at least 21 localist school groups have been set up through Facebook, including 16 that were reported earlier, in response to calls by activist group Studentlocalism. Another group had closed its Facebook page.

New concern groups have emerged on Facebook in the past week, including one from Tung Chung Catholic School and another from Wong Cho Bau Secondary School operated by the pro-Beijing Hong Kong Federation Of Education Workers.

Tony Chung Hon-lam, a Studentlocalism convenor, said more recruits were signing up for his group, from “sometimes not even one a week” to five or six a week, after it came into the spotlight. The group has imposed a tight vetting system for members, requiring them to fill forms with details of their Facebook and Instagram accounts for background checks.

Those who insisted on only rational, non-violent action would be rejected, he explained.

Chung would not rule out the use of violence to achieve their goals. A spokesman of a localist student concern group at Munsang College in Kowloon also told the Post it supported “any means of action in order to defend our autonomy”.

But Degas Chan Pui-chung from a localist organisation at Ying Wa College in Kowloon said his group was against the use of violence as it believed secondary school pupils were too young to be exposed to such dangers.

It is understandable that young people get frustrated about the current situation in Hong Kong, but independence cannot solve all problems

Executive councillor Fanny Law Fan Chiu-fun

Fanny Law, a former top education official, called on a radio programme for pro-independence groups to be banned from schools, and their representatives to be stopped from leading student unions .

Law, a close adviser to Chief Executive Leung Chun-ying, said the historical context of discussing independence was “too complicated” for schools, and that secondary school students could be misled without a thorough understanding of context, such as the First Opium War and the drafting process of the Basic Law, the city’s mini-constitution.

“It is understandable that young people get frustrated about the current situation in Hong Kong, but independence cannot solve all problems,” she said.

Law also urged teachers to avoid bringing up the topic during class discussions and suggested that the family backgrounds of students advocating independence campaigns should be looked into to better understand what was driving them towards such taboo talk.